The present invention relates to a method and apparatus for encapsulating a semiconductor device disposed on a substrate as part of a semiconductor packaging process.
When manufacturing semiconductor devices, a large number of devices are laid out on a large substrate. To improve manufacturing efficiency, there is a tendency for even more devices to be laid out on the same substrate. This has increased the density of devices on a substrate. Generally, as shown in FIG. 1, semiconductor devices 10 are laid out in an array on a substrate 12. Each semiconductor device 10 on the substrate 12 is covered with a mold material. There are various ways to cover the devices with the mold material. For example, referring to FIG. 2, two or more (e.g., four) semiconductor dies 14, 16, 18, and 20 are stacked and encapsulated with a mold compound 22 to form a single one of the devices 10. The device 10 is referred to as a stacked die.
There are various machines available to mold the devices 10 on the substrate 12. A conventional molding apparatus is described in U.S. Pat. No. 3,412,431. This molding apparatus uses a deposition/spray method to spray mold material from a nozzle and deposit the mold material onto a molding subject. However, with the deposition/spray method, as the density of devices on a substrate increases, a mold void or incomplete fill may be formed between the substrate and semiconductor die. This problem is particularly critical with stacked die devices. Accordingly, it is difficult to mold a substrate (device) without causing mold voids, incomplete fills, or wire sweeps. Defective molding lowers the yield of semiconductor products, which increases the time and cost of production. The deposition/spray method also has a tendency of wasting the mold material.